ISC2 Certified Secure Software Lifecycle Professional (CSSLP) Practice Question

You are defining security architecture for an industrial controller that loads device drivers and BIOS updates at power-on. Compliance requires preventing execution of tampered or unauthorized code. Which mechanism MOST effectively provides both integrity and authenticity assurances before the firmware and drivers run?

Activate the operating system's kernel-mode code signing policy to block unsigned drivers after the OS has loaded.
Schedule periodic offline malware and vulnerability scans of firmware and driver binaries using signature-based tools.
Compute a CRC32 checksum for every firmware image at boot and compare it with a value stored on the system drive.
Enable hardware-enforced secure boot that validates cryptographic signatures of each firmware and driver against a root-of-trust key during the power-on sequence.

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Answer Description

Hardware-based secure boot establishes a root of trust anchored in immutable code or keys burned into the platform. Each firmware component and driver is cryptographically signed; during the boot sequence the platform verifies the signature against trusted public keys before allowing execution. This process detects any modification (integrity) and confirms the publisher's identity (authenticity). A simple CRC stored on local media can show bit-level changes but does not prove who produced the code and is itself susceptible to tampering. Enforcing driver signing after the OS loads protects only kernel modules, leaving earlier firmware stages unchecked. Periodic vulnerability scans may uncover known malicious code long after it has already executed and do not provide real-time integrity or authenticity guarantees.

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